URUMQI, China — As police with riot clubs patrolled nearby, a merchant whispered that he feared a sweeping crackdown in China's northwestern Muslim region once the Olympic spotlight fades.

This photo taken Aug. 4, 2008 in Kashgar city in China's Xianjiang province and made available Sunday Aug. 17, 2008 shows the scene of an attack, where according to China's state-run Xinhua News Agency, two men rammed a dump truck into a group of jogging policemen. The assailants plowed into the policemen performing their morning exercises outside the the Yijin Hotel next to their paramilitary border patrol station. The report said after the truck hit an electrical pole, the pair jumped out, threw handmade explosives at the barracks and "also hacked the policemen with knives." Sixteen police were killed in the attack, Xinhua reported. (AP Photo/Str)

"After the Olympics, the government will waaaaah!" said the Muslim businessman, grimacing and using his hands to make a gesture as if he were strangling someone. He would only give part of his name, Enwer, because he feared arrest if caught talking to a reporter about the issue.

Residents and human rights groups fear the Chinese government will crack down after the Olympics to punish Xinjiang for three deadly breakouts of violence this month, including an attack that killed 16 police officers. The assaults, which claimed 31 lives, came as China was trying to use the Olympics to present itself as a modern, powerful and harmonious nation.

This isolated region is home to China's ethnic minority Uighurs, who say they are repressed by the Chinese government. For its part, the Chinese government insists that it is fighting terrorism rather than suppressing ethnic minorities.

"Terrorism is a criminal activity of very few people," Mao Gongning of the State Ethnic Affairs Commission said at a news conference Saturday in the Chinese capital. "It is not a problem related to ethnicity or religion."

Human rights groups worry, however, that repression could begin as the Summer Games close on Sunday and the tourists, athletes and foreign media depart.

Mark Allison, China researcher for the rights group Amnesty International, said the assailants should be arrested and brought to justice. But he added that China has a history of using security threats in Xinjiang as an excuse for much broader crackdowns on human rights in the region.

"We can see from examples of closures of several mosques over the recent years, very strict control over religion and also arrests of activists as well as people accused of violent offenses," he added.

One of the most severe and well-known crackdowns came after a major protest in February 1997 in the western city of Yining, where Uighurs were upset about restrictions on religion and culture. After security forces put down demonstrations, thousands of Uighurs were arrested, mosques were closed and public security rallies were held across the region, according to the U.S.-based Human Rights Watch.

One shopkeeper in the Xinjiang county of Kuqa — scene of one of this month's attacks — said last Saturday that he was bracing for heavy-handed measures. The man, who declined to give his name because he feared retribution, was a Uighur, a member of the Turkic ethnic minority whose members were accused of carrying out the recent attacks.

"Usually if a Uighur gets in trouble, the police come and detain everyone in his family. Then they lose their jobs and have trouble getting new ones," the man said.

China has shown itself to be capable of such retaliation in its handling of another restive region, Tibet. After violent riots five months ago, Tibetan areas are still closed off to foreign reporters and most overseas tourists.

The Dalai Lama — Tibet's spiritual leader who typically uses diplomatic tones when speaking about the Chinese government — accused Beijing of torturing Tibetans during the Olympic games.

"Unfortunately the Olympic spirit is not at all respected by Chinese officials inside Tibet," he said in an interview Saturday with a television station in Paris. "There are restrictions on the circulation of information, a very strong censorship. And often civilians are arrested and tortured very violently, to the point where they die."

The recent wave of assaults in China's northwest surprised many because they came amid tight security for the Olympics, and after a decade of relative calm.

After the first brazen assault on Aug. 4, photos obtained by The Associated Press showed six bodies on the ground and a dump truck the assailants used to ram the police tilting on its side.

In the aftermath, an Islamic militant group issued a video warning Muslims to avoid public transportation during the Olympics. They claimed mistreatment of Muslims justified holy war and accused China of forcing Muslims into atheism by killing Islamic teachers and destroying Islamic schools.

Six days after the attack, another group of bombers struck in Kuqa, where 12 people died. Knife-wielding assailants killed three more people last Tuesday at a checkpoint outside Kashgar.

No group has taken responsibility or described the motives for this month's attacks in Xinjiang.

The violence was still being discussed with hushed voices Saturday in the back alleys of Xinjiang's capital, Urumqi, where dried snake skins hung from drugstore windows and men sharpened butcher knives with whirling grinders.

One jade dealer who would only give part of his name, Mehment, because he feared the police, said Xinjiang was heading for another dark period. "Revenge. Yes, there will be revenge," he said.

Urumqi is now dominated by the Han — China's ethnic majority — who have been flooding into the remote metropolis.

Many Uighurs are concerned about a high degree of self rule in the territory, said S. Frederick Starr, chairman of the Central Asia-Caucasus Institute at Johns Hopkins University.

"The Chinese response is that, `If you put aside this nonsense we will make you wealthy,'" said Starr. He said he doubted Beijing would relax control of Xinjiang anytime soon.